C. Cruces Blanco

Derivative spectrophotometric resolution of mixtures of the food colourants Tartrazine, Amaranth and Curcumin in a micellar medium.

Abstract A study of the absorption spectra of the food colourants Tartrazine (E-102), Amaranth (E-123) and Curcumin (E-100) in various organic solvents and pH media, have been carried out. In addition, the spectral behaviour in aqueous micellar systems of anionic, cationic and non-ionic surfactants, as well as β -cyclodextrin, was investigated. Analytical methods are proposed for the determination of the three dyes in mixtures without any prior separation step, by the application of the derivative technique to the normal absorption spectra, based on the use of cetyltrimethylammonium bromide (CTAB) in 0.1 M NaOH, over the concentration range 2–50 μg ml −1 . The methods are applied for determining the three dyes in commercial food products.

Enhanced fluorimetric determination of procaine in pharmaceutical preparations by aqueous β- cyclodextrin inclusion and non-aqueous competitive action

Abstract The effects of changes in polarity and dielectric constant of the solvent on the fluorescence of procaine hydrochloride in different solvents, and in β-cyclodextrin (β-CD) and micellar media (cetylpyridium chloride and sodium dodecyl sulphate), are described in detail. It is shown that, with N,N -dimethylformamide as solvent procaine is better incorporated in β-CD and micelles. Methods are developed under these conditions based on normal, synchronous first- and second- derivative fluorimetry. The linear dynamic range is 10–680 ng ml -1 and the detection limit is 2.5 ng ml -1 ; the relative standard deviation is 0.68% for the β-CD method with normal fluorimetry. The methods are applied directly to the determination of procaine in different pharmaceutical preparation with recoveries of 88–108%.

Fluorometric Determination of Folic Acid Based on Its Reaction With The Fluorogenic Reagent Fluorescamine

Abstract A spectrofluorimetric analysis of folic acid (pteroylglutamic acid) using fluorescamine as a fluorogenic reagent, has been developed. The analytical parameters for optimal reaction and sensitivity (pH, fluorescamine concentration, temperature, reaction time), have been studied. The present method may be employed for the analysis of small amounts of folic acid (< 20 ppb), without interferences from other compounds; the selectivity being increased by the application of the synchronous derivative technique to normal fluorescence spectra. The minimum detectable quantity, using the latter technique, is estimated to be 16 ppb, with a relative standard deviation of 2.7 % (10 determinations). A soft sport beverage, containing low concentrations of the vitamin, have been satisfactorily analyzed.

Determination of carbaryl and its metabolite 1-naphthol in commercial formulations and biological fluids

A simple and sensitive method for the determination of carbaryl in whole blood and commercial formulations, based on normal, and synchronous first- and second-derivative fluorescence spectra, is presented. Solvent effects on the spectral characteristics of carbaryl solutions and the influences of instrumental parameters are described in detail. Two methods have been developed, with neutral (for carbaryl) and basic (for 1-naphthol) media. Detection limits of 0.9 and 0.7 ng/ml were achieved for carbaryl and 1-naphthol, respectively, with the first-derivative approach.

Determination of the Drug Naphazoline in Pharmaceutical Preparations by Heavy Atom-Induced Room-Temperature Phosphorescence

A simple, selective, and sensitive heavy atom-induced room-temperature phosphorimetric method (HAI-RTP) is described for the determination of naphazoline (NPZ) in pharmaceutical preparations. The phosphorescence signals are a consequence of intermolecular protection when analytes are, exclusively, in the presence of a heavy atom salt and sodium sulfite as an oxygen scavenger to minimize RTP quenching. This variable selection constitutes the basis of the HAI-RTP method for the determination of naphazoline (detection limit 43.5 ng/mL; 2.39% relative standard deviation at 500 ng/mL). The method has been applied to the analysis of pharmaceutical preparations.

Micellar medium for the analysis of complex mixtures of molybdenum and tungsten by derivative synchronous spectrofluorimetry in steels

The cationic surfactant hexadecyltrimethylammonium bromide enhances the fluorescence intensity of both molybdenum and tungsten complexes obtained with Alizarin Red S. This characteristic has been used for a sensitive simultaneous spectrofluorimetric determination of both ions over the range 32-4000 ng/ml and 49-2500 ng/ml for Mo and W, respectively. Good selectivity is achieved applying the well known synchronous derivative technique with a minucious pH selection. The proposed method has been applied to a certified steel sample with recoveries between 96 and 102%.

Simple determination of propranolol in pharmaceutical preparations by heavy atom induced room temperature phosphorescence.

The applicability of heavy atom induced room temperature phosphorescence in real samples is demonstrated in this work. In this methodology only two reagents, potassium iodide as heavy atom salt and sodium sulphite as oxygen scavenger, were used to obtain phosphorescent signal of propranolol in solution. Thus a new simple, rapid and selective phosphorimetric method is proposed for propranolol determination in pharmaceutical preparations. The phosphorescence intensity was measured at 492 nm exciting at 294 nm. Phosphorescence was fully developed instantly, obtaining a linear concentration range between 0 and 500 ng ml 1 with a detection limit of 14.4 ng ml 1 , an analytical sensitivity of 6.7 ng ml 1 and a standard deviation of 1.4% at a 300 ng ml 1 concentration level. The method has been successfully applied to the analysis of propranolol in an antidepressive pharmaceutical preparation and it was validated using standard addition methodology. # 2002 Elsevier Science B.V. All rights reserved.

Simultaneous Determination, by Capillary Zone Electrophoresis, of Multiple Components of Different Industrial Products

Four parabens (esters of 4-hydroxybenzoic acid), effective preservatives against the growth of bacteria, yeast, and mold in numerous industrial products, have been used in this work as model compounds to demonstrate the resolving power of capillary electrophoresis (CE). The simultaneous determination of methyl-(MP), ethyl-(EP), propyl-(PP), and butylparaben (BP) was achieved by capillary zone electrophoresis (CZE) with UV diode-array detection at 294 nm. When run voltage, temperature, and electrolyte concentration and pH were optimized the most effective separation was achieved within 7 min by use of 50 cm (effective length) fused silica capillary tubing and operation at 25kV and 20°C. Background electrolyte comprising 35 mM tetraborate buffer adjusted to pH 10.0 gave the best results. The limits of detection of the optimized method ranged from 0.65 μg mL−1 for BP to 0.81 μg mL−1 for MP; the relative standard deviation was between 0.35 and 0.50%. These results showed that the method enables the determination of the four parabens in commerially available cosmetic and pharmaceutical preparations containing some of the parabens and in an unidentified canned berry fruit juice.

Isodifferential Derivative Spectrophotometric Assay of the Carbamate Pesticide Carbaryl and its Metabolite in Biological Fluids and Commercial Formulations

Abstract Two types of applications (biological fluids and commercial formulations) have been used to demonstrate the advantages of UV derivative spectroscopy using the isodifferential assay for the quantitative simultaneous determination of the insecticide carbaryl and its metabolite 1-naphthol. By a careful selection of the working wavelengths based on the graphical model to measure derivative amplitudes, it is possible to determine both compounds in the range of 0.2–40.0μg/ml in presence of five and ten-fold concentration excess, respectively. Accurate and reproducible results are obtained with no preliminary separation step required.

Simultaneous spectrofluorimetric determination of traces of molybdenum and boron in plant leaves

Abstract A method is described for the simultaneous determination of molybdenum and boron in plant leaves, based on the highly sensitive fluorescence reaction with Alizarin Red S. Simplicity is achieved by using first and second derivatives of the synchronous spectra. Appropriate calibration equations were established between 0.1–0.9 and 0.3–0.7 μg ml−1 for molybdenum and boron, respectively, with a mean relative standard deviation of 2.2%.